The invention has its background in problems associated with known structures and methods of expanding, setting, fixing and/or loosening such a packer body relative to an external object, for example a tubular body or a hole wall. It is in particular a question of problems that may arise when the packer body is subjected to great stresses during setting and/or use, for example great axial forces, high pressure, high temperature, erosive particles and/or a chemically aggressive environment. Such conditions may arise, for example, when the packer body is used in connection with an underground well at sea or on shore, for example in a petroleum well.
Under such extreme conditions, the elastic/plastic packer body may, inter alia, extrude or flow into accessible cavities in the proximity of the packer body, for example into cavities in the proximity of the packer body lengthways and/or widthways. Such extrusion is normally the more pronounced the larger the expansion and/or stresses to which the packer body is subjected during setting and/or use. As a rule, this extrusion is undesired and may weaken, possibly completely or partially ruin, the packer body. This may entail, inter alia, poor sealing function during use, possibly the packer body sticking completely to, possibly wedging against, said external object. It may thereby be difficult to loosen the packer body after use, the packer body possibly also getting torn to pieces and becoming ruined by such loosening. In a subterranean well, such a weakened packer body may constitute an incomplete pressure barrier which is possibly associated with pressure/fluid leakage and poor pressure control.
Another property of such an elastic/plastic packer body is that when the packer body is being compressed, expanded and set/used, energy is being stored in it. It is this stored energy that provides for the packer body to be pressed sealingly against said external object. However, the extreme conditions mentioned may result in the packer body disintegrating, eroding or being crushed into pieces, so that the packer body unintentionally loosens.
There is thus a need in the industry for devices that prevent extrusion and/or disintegration of such a packer body during setting and/or use.